The long-term aim is a better understanding of the auditory processes that enable hearing in background noise, and the effect of early hearing loss on those processes. Aim 1 will investigate the hypothesis that the development of the ability to integrate spectro-temporal glimpses of speech in noise has a protracted development in normal-hearing children, and that such development is even more protracted in children who have long histories of recurrent otitis media with effusion (OME). Aim 2 investigates the relatively novel perspective that hearing loss is associated not only with delays in development and the attenuation of auditory cues, but may also be accompanied by adaptations in auditory processing that enable efficient use of available remaining information. This will be examined both in patients having OME and patients who have severely sloping sensorineural hearing losses. Aim 3 investigates the processing of binaural and monaural acoustical information in patients having severe, unilateral conductive hearing losses. The binaural experiments are aimed at testing how a long history of unilateral hearing loss affects the ability of the brain to analyze and weight information from the two ears. The monaural experiments will investigate whether relatively complex monaural processing is impaired in the ear having history of conductive hearing loss. In patients receiving hearing loss intervention, the binaural and monaural abilities will be tracked longitudinally to determine whether experience results in changes in the ability of the auditory system to weight and analyze information from the two ears. Psychoacoustic studies will use standard, adaptive testing techniques, and speech studies will use a combination of adaptive and fixed block methods. All phases of the project will include age-matched control listeners. Data will be analyzed using analysis of variance and descriptive statistical procedures. There are two ways in which the proposed work relates to public health: 1) the data from the studies on hearing loss will provide information about the effect of early hearing loss on the development of auditory perception; 2) the studies on hearing abilities in normal-hearing children and adults will provide information about human abilities to hear signals in noise, the most common problem experienced by patients having hearing losses.